[MINOR] Optimize queue in memory manager

MERGE REQUEST

MR Guidelines

Overview

Similar to the optimization we recently added to the job queue, this MR optimizes the memory request queue to allow for easier garbage collection.

Checklist

Review and complete the checklist to ensure that the MR is complete before assigned to an approver.

• All new methods or updated methods have clear docstrings
• Testing added or updated for new methods
• Any new packages are added to Makefile and .gitlab-ci.yml
• API documentation updated for API updates
• Module README.md updated for changes to workflow
• Issue added to Sia-UI repo for new supporting features
• Changelog File Created

Issues Closed